Seal for push button actuated device



A ril 25, 1967 D. E. CLARKE ETAL 3,316,379

SEAL FOR PUSH BUTTON ACTUATED DEVICE Filed July 29. 1965 r 2Sheets-Sheet l PRIOR ART fnventam': David E, ('Zariie, avid L.Eisr20r,

April 25, 1967 D. E. CLARKE ETAL 3,316,379

SEAL FOR PUSH BUTTON ACTUATED DEVICE Filed July 29, 1965 2 Sheets-Sheet2 Fig. 2, fig. 5..

Inventors: ,Davz'd E. Clarita, David L. E'zlsrzor,

v mdg mw United. States Fatent G 3,316,379 SEAL FOR PUSH BUTTON ACTUATEDDEVICE David E. Clarke, Attleboro, and David L. Eisnor, Norton, Mass.,assignors to Texas Instruments Incorporated, Dallas, Tex., a corporationof Delaware Filed July 29, 1965. Ser. No. 475,675 6 Claims. (Cl.200-168) This invention relates to electrical switches and, moreparticularly, to a fluid-tight seal for a push button actuatedelectrical switch.

It is an object of this invention to provide a seal to protect theinterior switch parts from the deleterious effects of splashed water,oil, or other fluids or matter.

It is also an object of this invention to provide such a seal in whichno deleterious interference occurs between the seal and the push buttonto affect the operation of the push button or the switch.

Other objects will be in part apparent and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction and arrangements of parts which willbe exemplified in the structures hereinafter described and the scope ofthe application of which will be indicated in the appended claims.

In the accompanying drawings in which one of the various possibleembodiments of the invention is illustrated:

FIG. 1 is a sectional, partly fragmentary view of a seal according tothe instant invention;

FIGS. 2 and 3 are views similar to FIG. 1 showing the seal in variousstages of deformation;

FIG. 4 shows an example of a seal according to prior art;

FIG. 5 is an enlarged view similar to a portion of FIG. 1 showing amodification of the device; and

FIG. 6 is an enlarged view similar to a portion of FIG. 1 showing athird modification of the device of FIG. 1.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Dimensions of certain of the parts as shown in the drawings have beenmodified for the purpose of clarity of illustration.

In certain types of electrical switch structures which employ a housingin which the parts of the electrical switch are contained therein, andin which a push button is employed which moves reciprocally in and outof the housing to permit manual actuation or resetting of the switch andto provide an indication of the condition of the switch, it is desirableto provide a seal to protect the entrance of foreign matter such aswater, oil, dust and the like into the interior of the switch housing.An example of such a switch is shown in copending application Ser. No.317,489, filed on Oct. 21, 1963, now Patent No. 3,257,523, in the nameof David E. Clarke and assigned to the assignee of the instantinvention.

Referring now to the drawings, there is shown in FIG. 1 one embodimentof the instant invention. A fragmentary portion of a switch includingthe seal according to the instant invention is shown in fragmented formand is generally indicated by reference numeral 10. Switch 10 includes ahousing 12 and the bushing 14 which provides an entrance (not shown) tothe interior of housing 12 and which permits a push button 16 to movebetween the solid line extended position shown in FIG. 1 to the dottedline depressed position shown in FIG. 1.

If desired, push button 16 may include at its distal end 18, acircumferentially extending flange 20 which permits easier manual graspof the push button for manually moving it from the depressed, dottedline position shown in FIG. 1 to the extended solid line position.

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Mounted on bushing 14 is a sealing enclosure 26 which surrounds the pushbutton 16. Enclosure 26 includes a tubular portion 25 and a closureportion 30 formed on the outer distal end of tubular portion 25.Enclosure 26 is formed of a suitable, flexible and resilientlydeformable material such as rubber.

In the embodiment shown in FIG. 1, switch 10 is retained in operatingposition on a mounting panel 21 having an aperture therein through whichbushing 14 projects. Bushing 14 in the embodiment of FIG. 1 is threadedto receive a threaded nut 22. Nut 22 includes a radially extendingprojection or flange 23.

Enclosure 26 includes at its inner proximal end, at which it is mountedon the bushing 14, a radially extending skirt portion 27 which includesa groove 28 which mates with the radially extending projection 23 of nut22 and about which the skirt is molded. As nut 22 is screwed down thatportion of skirt 27 adjacent the mounting plate 21 is pressed againstthe mounting plate to form a tight seal therebetween.

It will be understood that the walls of tubular portion 25 aresutficiently thin to permit easy manual deformation thereof such thatpush button 16 may be grasped and manually actuated for movement fromthe depressed position to the extended position as shown in FIG. 1.

It will be noted that the inner diameter and inner axial dimension ofthe enclosure 26 are sufficiently large by comparison with thecorresponding external diameter of the flange 20 of push button 16 andthe axial dimension of push button 16 such that the push button is ableto move between its solid line extended position and its dotted linedepressed position when the enclosure 26 is in its undeformed state. Itwill be understood that, in some cases, the inner axial dimensions ofenclosure 26 may be equal to or slightly smaller than the axial extentor dimension of button 16 when a downward biasing force on the button inthe extended position is unimportant.

Closure 30 includes, at a portion centrally located about the axisrunning lengthwise along tubular portion 25, a thickened knob 32 formedthereon. The thickness of knob 32 exceeds the thickness of the wall oftubular portion 25 by an amount suflicient to permit the upper surfaceof knob 32 to project above the collapsed position of enclosure 26. Thatportion of closure 30 not occupied by knob 32, and which surrounds knob32 at 29, has an axial thickness and radial extent sufiicient, inrelation to the thickness of the wall of tubular portion 25 and thediameter of knob 32, to permit portion 29 to be the weakest portion ofenclosure 26, when the knob 32 is subjected to a force in the verticallydownward direction as viewed in FIG. 1.

In those cases where the diameter or transverse dimension of knob '32 isapproximately equal to the interior diameter or transverse dimension oftubular portion 25 diminished by an amount equal to twice the thicknessof the wall of tubular portion 25, and the radial extent of portion 24is consequently relatively small, the axial thickness of portion 29 isless than the transverse dimension or thickness of the wall of thetubular portion 25. Where the diameter of knob 32 is substantiallysmaller than the interior diameter of tubular portion 25 as diminishedby twice the thickness of the wall of tubular portion 25, the axialthickness may be equal to or slightly thicker than the thickness of thewall of tubular portion 25. In any event, the diameter of knob 32, theaxial thickness of portion 29 and the radial or transverse thickness ofthe wall of the tubular portion 25, are related such that in the face ofa force directed downwardly on the upper surface of knob 32, the weakestportion of enclosure 26 and consequently the first portion to deformwill be at portion 29 as will be further described in connection withFIGS. 2 and 3.

. 26 can best be 'seen in FIGS. 2 and 3.

It is believed that the operation of and advantages of applicantscontribution can best be understood by examining the operation of atypical prior art device such as that shown in FIG. 4. In that device,enclosure 62 is similar to enclosure 26 in that it is mounted on abushing 14 and encloses a push button 16 forming a portion of a switchsuch as that described in the aforementioned copending application ofClarke and which can move freely between positions similar to thoseshown in solid and dotted lines in FIG. 1. I

To set the switch as is described in the aforementioned application toClarke, push button 16 must be depressed by manually exerting force onthe distal end 18 of button 16. In the push button sizes contemplated inthis application, the area of the manual'digit used to actuate button 16would exceed the area of closure 60 or at least would overlap a portionof the circumferential edge thereof.

In actuating button 16 downwardly as seen in FIG. 4,

it has been found that enclosure 62, and particularly the tubularportion 25 thereof, when made thin enough to permit manual grasp of thebutton 16 deforms in such a manner that convolutions 63 directedradially inwardly toward button 16 are formed.

Some of these convolutions 63 which bulge inwardly abut and frictionallyengage the surface of the push button 16. Where the push button includesa flange 18, such convolutions can abut and engage the lower portion ofthe flange to exert a force having the deleterious effect of tending tourge the button 16 toward the extended position. Further, in someconstructions, the convolutions can form prior to the positioning of thebutton 16 in the .stable, depressed or fully reset condition and thusprevent the manual resetting of the switch. Another deleterious effectof these convolutions is that they are inclined to change the parameterswithin which the switch will operate by the exertion of non-manualforces on the push.

button 16.

With this background, the advantages of applicants device will be seen.The operation of the enclosure seal It will be noted that as a force isapplied in a downward direction, as viewed in FIGS. 2 and 3, to thedistal end of the enclosure 26, this force, even though exerted by aninstrument having a surface area greater than that of the distal end ofenclosure 26, will be exerted on knob 32 only and not on the remainderof the surface of closure 30. As a result the force will be centeredabout the central axis running lengthwise through tubular portion 25andenclosure 26. Since, as noted, the weakest portion of enclosure 26 isat portion29 of closure 30, the first deformation occurs at portion 29and as the force on knob 32 increases and the push button moves from thesolid line position toward the dotted line position as shown in FIG. 1,thereafter, the walls of tubular portion 25 deform and bulge outwardlyin a radial direction from the axis of tube 25 and away from the pushbutton 16. It will be seen that as this force continues, the bend linemoves down the walls of tube 25 toward the inner end of tubular portion25 to permit further bulging in an outward direction. It will be alsonoted that at no time during the period in which the push button passesfrom the solid line to the dotted line position through the FIG. 2 andFIG. 3 positions are convolutions formed which bulge inwardly in aradial direction or towards the push button 16.

-In some cases, it is desirable to enable visual detection of thecondition of switch by viewing button 16,

as is described in the aforementioned application of an upper portionand a lower portion 40 between which the projection 24 of the nut 22 isinserted. In the FIG. 6 configuration, a flange 42 is provided on thebushing itself and nut 22 is dispensed with. In this embodiment,

solution because in such a case manual grasp of button 16'would beprevented. 1

It will be understood that the actuating force which has been describedas'manual need not be manual but can be any external, mechanical orother actuating mechanism.

It will be noted that the problems solved by applicants device can notbe solved by enlarging the diameter of the bushing and hence theenclosure, since in most switch applications these dimensions must bekept small to permit compact mounting of multiple switches. Further, anenlarged bushing and enclosure would render manual grasp of the button16 in the depressed condition diflicult or impossible.

In view of the above it will be seen that the several objects of theinvention are achieved and other advantageous results are obtained.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangements of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also, it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

As 'many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings, shall be interpreted as illustrative and not in a limitingsense, and it is also intended that the appended claims shall cover allsuch equivalent variations as come within the true spirit and scope ofthe invention.

We claim: 7

1. In a push button operated switch having a housing, a bushingproviding an entrance to the interior of the housing, and a push buttonpositioned in the bushing for reciprocating movement therewithin betweena depressed position and an extended position, a device for sealing theinterior of the housing from fluid, dust and the like comprising, anenclosure mounted at its inner end on the bushing in fluid-tightrelationship therewith and enclosing the push button, the enclosurehaving interior transverse and axial dimensions sufliciently large incomof the enclosurein the exterior of the closure, the exterior knobhaving a transverse dimension less than the interior transversedimension of the enclosure whereby an actuating force applied to theclosure at the distal end of the enclosure to actuate the push buttonare centered about an axis running lengthwise along the enclosure topermit, upon application of the actuating force, the walls of theenclosure to bulge in a direction away from the push button and toinhibit the formation of convolutions of the enclosure walls in adirection toward the interior of the push button.

2. In a push button operated switch having a housing,

a bushing providing an entrance to the interior of the housing, and apush button positioned within the entrances in the bushing forreciprocating movement in an axial direction therewithin between adepressed position and an extended position, the push button having acircumferentially extending flange at the distal end thereof tofacilitate manual grasp of the push button, a device for sealing theentrance and protecting the interior of the housing from fluid, dust andthe like comprising a manually deformable enclosure including a tubularportion mounted at its inner end on the bushing in fluid-tightrelationship therewith, the tubular portion of the enclosure having aninterior diameter and axial dimension exceeding the exterior diameterand axial dimensions respectively of the push button flange to permitreciprocal movement of the push button within the enclosure, the wallsof the tubular portion of the enclosure being relatively thin to allowmanual deformation thereof to enable grasp of the flange of the pushbuton to permit manually actuated movement of the push button from thedepressed position to the extended position, the enclosure having aclosure portion formed on the distal end thereof, the closure for thedistal end of the enclosure having walls thinner than the walls of thetubular portion of the enclosure, the closure having a thickened knoblocated centrally about the axis of the tubular portion of the enclosureon the exterior surface of the closure, the knob having a diameter lessthan the interior diameter of the tubular portion of the enclosure by anamount exceeding the thickness of walls of the closure and a thicknessexceeding the thickness of the walls of the tubular portion, such thatforces applied to the closure at the distal end of the enclosure toactuate the push button by an instrument having a surface area greaterin extent that the corresponding surface area of the closure arecentered about the axis running lengthwise along the tubular portion ofthe enclosure whereby, upon application of such forces to the closureend to move the push button to the depressed position, the initialdeformation of the enclosure takes place at the portion of the closureunoccupied by and surrounding the knob to permit the tubular walls ofthe enclosure to bulge in a direction away from the push button and toinhibit the formation of convolutions of the enclosure walls extendingin the direction of the push button.

3. A device as set forth in claim 2 wherein the enclosure is formed of atransparent material and the push button includes an indicator visiblethrough the enclosure to indicate its position.

4. A device as set forth in claim 2 wherein the outer portion of thebushing includes a flange and the inner end of the tubular portionincludes a flared portion having a groove therein which receives thebushing flange to seal the enclosure and the bushing.

5. In combination, a push button operated switch including a housing, abushing providing an entrance to the interior of the housing, a pushbutton positioned Within the entrance in the bushing for reciprocatingmovement in an axial direction therewithin between a depressed positionand an extended position, the bush button having a circumferentiallyextending flange at the distal end thereof to facilitate manual grasp ofthe push button, a device for sealing the entrance and protecting theinterior of the housing from fluid, dust and the like comprising amanually deformable enclosure having a tubular portion mounted at itsinner end on the bushing in fluid-tight relationship therewith, thetubular portion of the enclosure having an interior diameter and axialdimension exceeding the corresponding dimensions of the push buttonflange to permit reciprocal movement of the push button within theenclosure, the walls of the tubular portion of the enclosure beingrelatively thin to allow manual deformation thereof to enable grasp ofthe flange of the push button to permit manually actuated movement ofthe push button between the depressed position to the extended position,the enclosure having a closure portion formed on the distal end thereof,the closure for the distal end of the enclosure having walls thinnerthan the Walls of the tubular portion of the enclosure, the closurehaving a thickened knob located centrally about the axis of the tubularparts of the enclosure on the exterior surface of the closure, the knobhaving a diameter less than the interior diameter of the tubular portionof the enclosure by an amount exceeding the thickness of walls of theclosure and a thickness exceeding the thickness of the walls of thetubular portion, such that forces applied to the closure at the distalend of the enclosure to actuate the push button by an instrument havinga surface area greater in extent than the corresponding surface area ofthe closure are centered about the axis running lengthwise along thetubular portion of the enclosure whereby, upon application of suchforces to the closure end to move the push button to the drepressedposition, the initial deformation of the enclosure takes place at theportion of the closure unoccupied by and surrounding the knob to permitthe tubular walls of the enclosure to bulge in a direction away from thepush button and to inhibit the formation of convolutions of theenclosure walls extending in the direction of the push button.

6. In the combination set forth in claim 5, a nut threadedly engagedwith the bushing and the proximal end of the enclosure being moldedaround the nut to permit mounting the enclosure in the bushing bythreaded engagement.

References Cited by the Examiner UNITED STATES PATENTS 2,795,144 6/1957Morse 2001 68 3,054,879 9/1962 Soreng 200-168 3,246,112 4/1966 Adams200-168 OTHER REFERENCES 1,049,465, Breuer (German application), January1959. 1,059,072, Breuer (German application), June 1959.

ROBERT K. SCHAEFER, Primary Examiner, H. O. JONES, Assistant Examiner,

1. IN A PUSH BUTTON OPERATED SWITCH HAVING A HOUSING, A BUSHINGPROVIDING AN ENTRANCE TO THE INTERIOR OF THE HOUSING, AND A PUSH BUTTONPOSITIONED IN THE BUSHING FOR RECIPROCATING MOVEMENT THEREWITHIN BETWEENA DEPRESSED POSITION AND AN EXTENDED POSITION, A DEVICE FOR SEALING THEINTERIOR OF THE HOUSING FROM FLUID, DUST AND THE LIKE COMPRISING, ANENCLOSURE MOUNTED AT ITS INNER END ON THE BUSHING IN FLUID-TIGHTRELATIONSHIP THEREWITH AND ENCLOSING THE PUSH BUTTON, THE ENCLOSUREHAVING INTERIOR TRANSVERSE AND AXIAL DIMENSIONS SUFFICIENTLY LARGE INCOMPARISON TO THE CORRESPONDING EXTERIOR DIMENSIONS OF THE PUSH BUTTONTO PERMIT RECIPROCAL MOVEMENT OF THE PUSH BUTTON WITHIN THE ENCLOSURE,THE WALLS OF THE ENCLOSURE BEING RELATIVELY THIN TO PERMIT MANUAL GRASPOF THE PUSH BUTTON, THE ENCLOSURE HAVING A CLOSURE FORMED ON ITS DISTALEND, THE CLOSURE HAVING A PORTION WEAKER THAN THE WALLS OF THE REMAINDEROF THE ENCLOSURE, THE CLOSURE HAVING A THICKENED KNOB LOCATED CENTRALLYABOUT THE AXIS OF THE ENCLOSURE IN THE EXTERIOR OF THE CLOSURE, THEEXTERIOR KNOB HAVING A TRANSVERSE DIMENSION LESS THAN THE INTERIORTRANSVERSE DIMENSION OF THE ENCLOSURE WHEREBY AN ACTUATING FORCE APPLIEDTO THE CLOSURE AT THE DISTAL END OF THE ENCLOSURE TO ACTUATE THE PUSHBUTTON ARE CENTERED ABOUT AN AXIS RUNNING LENGTHWISE ALONG THE ENCLOSURETO PERMIT, UPON APPLICATION OF THE ACTUATING FORCE, THE WALLS OF THEENCLOSURE TO BULGE IN A DIRECTION AWAY FROM THE PUSH BUTTON AND TOINHIBIT THE FORMATION OF CONVOLUTIONS OF THE ENCLOSURE WALLS IN ADIRECTION TOWARD THE INTERIOR OF THE PUSH BUTTON.